Polyamines (putrescine, spermidine, and spermine) are major cellular components, and have been shown to be involved in many systems related to growth and differentiation. Our current and older studies have been directed at learning how these polyamines are synthesized and regulated, and their physiological function. We have: (1) established the pathways for the biosynthesis of these amines in prokaryotes and eukaryotes and isolated the enzymes for the various steps in the pathways; (2) identified the genes responsible for each of the biosynthetic steps and constructed mutants with deletions in the various genes; (3) constructed plasmids that contain these genes and used the strains containing these plasmids to overproduce the encoded enzymes; (4) used the amine-deficient mutants to study the physiological effects of polyamine deprivation, including studies (in E. coli) on ribosome function, lamda replication and paraquat toxicity, and (in yeast) on growth population and maintenance of the double-stranded RNA killer virus; (5) sequenced the gene coding for S-adenosylmethionine decarboxylase in both E. coli and S. cerevisiae and the gene coding for spermidine synthase in E. coli; (6) demonstrated that S-adenosylmethionine decarboxylase is first formed as a proenzyme in both E. coli and yeast and is cleaved post-translationally with the conversion of serine to a covalently-bound pyruvoyl group that is essential for activity; and (7) studied the effect of site-specific mutagenesis on the conversion of the proenzyme to the active enzyme.